Bicycle-crank.



No. 631,276. Patented Aug. 22, I899.

J. BULVA.

BICYCLE CRANK.

(Application Bled Mar. 29, 1898.)

(No Modal.)

' UNITED STATES PATENT OFFICE.

JOSEPH BULOVA, on NEW YORK, N. Y.

BlCYCLE-CRANK.

SPECIFICATION formng part of Letters Patent No. 631,276, dated August 22, 189

Application filed March 29, 1898. Serial No. 675,529. (No model.)

T0 aZZ whom it may concern:

Be itknown that I, JOSEPH BULOVA, of New York cit-y, oounty and State of New York, have invented an Improved Bicycle-Cran k, of which the following is a'specification.

This invention relates to a crank for bicycles which is so oonstructed that the leverage from the pedal may be increased to a greater or less extent during the downstroke, so that it is in the power of the rider to adjust such leverage according to the steepness of the grade to be overcome, while on level roads the normal leverage may be retained.

In the accompanyingdrawings, Figure lis a side elevation of my improved bicycle-erank; Fig. 2, an elevation of the right crank, showing it in a different position; Fig. 3, a rear view, partly in section, of the right pedal and crank 5 Fig. 4, an inner view of a modification of the crank and Fig. 5, a rear view, partly in section, of the same.

The letter a represents the crank-arm of a bicycle keyed, as usual, to the driving-shaft Z); To the outer side of the free end of the arm a is connected a freely-revoluble link a by a pivot a3, which passes freely through the link a and is tapped into arm a. To the outer side of the free end of link a is in turn pivoted the pedal 0, which may have a tee-clip 0, if desired. Thusit may be seen that the link a is revoluble around arm a, While the pedal 0 is revoluble around the link a as well as around the arm a.

The parts et a are adapted to be interlocked at different angles during the downstroke by a ratchet-wheel d, made integral With 01' secured to the outer side of arm a around the pivot a Fig. 3, suoh ratchet-wheel having a series of teeth on its forward edge, while the te'eth on the rear edge may be otnitted. The ratehet-wheel is engaged by a pawl e, influenced by a spring 6 and pivoted to the inner side of link 61/. The ratchet-wheel d is thus placed at the onter end of the arm a concentrie to the pivot, and its diameter is considerably less than the length of the arm itself, so that the inner end of the link a is freely rotatable around the outer end of arm a and that the link Will be carried up by the arm during the upstroke of the latter.

In use the link a, with the pedal c, n01- mally depends at a from the arm a. VVhen the upper pedal has been earried somewhat beyond its uppermost position (upper pedal,

Fig. 1) and it is desired to increase the leverage, the foot is thrown out more or less, Fig. 2, in accordance With the increase of leverage desired. This throwing out of the foot Will cause the link a to be likewise swung outward and the pawl 6 to be carried over a greater or less number of the teeth of the ratchet 01 and to engage that one of the teeth With which it is ultimatelyin alinement. Thns it will be seen that a rigid connection between the parts et a is established and that the length of the leverage represented by the distance of the pedal 0 from the axle I) may be readily altered by the rider to eonform to the roadgrade, sneh leverage being readily changeable at every single downstroke. WVhen the pedal has arrivcd somewhat back of its lowermost position, (lower pedal, Fig. 1,) the arm et Will be revolved by the descent of the other foot and the pawl Will liberate the teeth of the ratchet-wheel, so that the link a will swing freely downward from pivot 61?. In this way the radius of revolution is againdecreased, and this diminished radius is maintained until the pedal has again passed its uppermost po sition, when the foot may be again throWn outward to increase the stroke radius, as here= tofore described.

On level roads or on downgrades where it is not desired to inerease the stroke radius the foot is not thrust forward at the beginning of the downstroke, but the link a is permitted t0 depend vertically from pivot a so that in this way no increase in leverage is produced.

Thus it will be seen that it is placed within the power of the rider to increase the leverage to any suitable extent, if he s0 desires, or to maintain the normal leverage, if that should be preferable.

In Fi'gs. 4 and 5 the pawl-andratchet mechanisrn is not looated between the parts a and 0/, but on the inner side 01: the part a. Here the pivot a is rigidly connected to the link a, but passes freely through arm a. On its inner end the pivot a carries the ratchet-wheel outer end of the link, and pawl-and-ratcheb mechanism, between the cran]; and the link, 10 to look the link to the erank in the act of forf, chat is Lhus revolved together with link a, and s engaged by the pawl g, pivoted to the innerside of arm aand influenced by springg'.

\Vhat I daim isward propulsion. 5 In a bicycle driving mechanism a crank- JOSEPH BULOVA.

shaft, a crank of normal length secured there- \Vitnessesz WILLIAM SCHULZ, F. V. BRIESEN.

00, a swinging link pivotally attached at the enter end of the crank, a peda1 pivoted to the 

